Changes in flow velocity patterns of the superior and inferior venae cavae during placental circulatory insufficiency
Bibliographic record
Abstract
OBJECTIVES: Placental circulatory insufficiency, expressed by the disappearance of the diastolic component of the umbilical artery Doppler velocity waveforms, causes blood flow redistribution that could disturb, to different extents, the systemic venous returns to the heart. The purpose of this study was to investigate the effect of an absence of diastolic blood flow in the umbilical artery on the relationship between the Doppler flow velocities of the venae cavae. METHODS: Fifteen normal fetuses (normal group) were matched for gestational age with 11 fetuses with absent diastolic flow in the umbilical artery (abnormal group). In the venae cavae, the following Doppler variables were measured and compared between groups: (a) during ventricular systole: maximum (S(max)) and minimum velocities (S(min)) and velocity integrals (SI); (b) during ventricular diastole: peak velocity of the E-wave and its integral (EI), the A-wave and its integral (AI). A venous velocity index (VVI) was defined as (S(max) + S(min))/S(max). RESULTS: In the normal group, S(min) and VVI were significantly higher in the inferior vena cava (IVC) than in the superior vena cava (SVC). The ratio SVC-VVI/IVC-VVI was therefore always less than one. In the abnormal group, S(min), SI, E, EI and VVI were higher in the SVC compared to those of the IVC. The ratio SVC-VVI/IVC-VVI was always greater than one. CONCLUSION: In the absence of umbilical artery diastolic flow, a reciprocal shift is observed between the IVC and SVC velocity waveforms characterized by a flow profile in the IVC which resembles that of a normal SVC profile and vice versa. These changes are another manifestation of blood flow redistribution towards the brain in the presence of placental circulatory insufficiency. They should be taken into account on Doppler assessment of ventricular diastolic function based on venous flow patterns during placental circulatory impairment.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".